Despite the serious nature of the exam, Tom seemed completely ___ about his preparation, spending most evenings watching TV instead of reviewing notes.
Acasual
Brelaxed
Cinformal
Dcomfortable
✓ 尽管考试性质严肃,汤姆对备考似乎完全漫不经心,大多数晚上都在看电视而不是复习笔记。
语境含批评意味(despite serious nature / watching TV instead of studying),需要表达「不认真/漫不经心」的负面含义,casual 最准确;relaxed 是正面的放松状态,不含批评。